Laser damage threshold studies on urea L-malic acid: A nonlinear optical crystal

Abstract

A detailed study of surface laser damage performed on a nonlinear optical crystal, urea L-malic acid, using 7ns laser pulses at 10Hz repetition rate from a Q-switched Nd:YAG laser at wavelengths of 532 and 1064nm is reported. The single shot and multiple shot surface laser damage threshold values are determined to be 26.64±0.19 and 20.60±0.36GWcm−2 at 1064nm and 18.44±0.31 and 7.52±0.22GWcm−2 at 532nm laser radiation, respectively. The laser damage anisotropy is consistent with the Vickers mechanical hardness measurement performed along three crystallographic directions. The Knoop polar plot also reflects the damage morphology. Our investigation reveals a direct correlation between the laser damage profile and hardness anisotropy. Thermal breakdown of the crystal is identified as the possible mechanism of laser induced surface damage.